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The strongest and most powerful athletes in the world do compound movements such as squats and power cleans, while the biggest bodybuilders in the world spend considerable time on isolation exercises such as preacher curls and seated calf raises. Practitioners in the fields of rehabilitation and functional training promote the use of both compound and isolation exercises. So how do you choose which type to use in your own program?

When it comes to program design, it’s critical to select the most appropriate exercises to achieve your goals for each training cycle. Here are eight guidelines to use when deciding between isolation and compound movements.

1. Isolation movements often don’t transfer well to performance in compound exercises. This is one of those times that the sum of the parts doesn’t equal the whole. For example, performing a training cycle of leg extensions and leg curls does not contribute significantly to improvements in squatting ability. In contrast, increasing your squatting poundages can significantly increase performance in leg extensions and leg curls.

2. Compound movements are usually less stressful on the body than isolation movements. Exercises such as squats and cleans can be performed year-round, because the stress of these compound exercises is distributed over many muscle groups. Isolation movements, in contrast, focus the stress on one area of the body and as such need to be varied more frequently to avoid overuse injuries. For advanced trainees, a good general guideline is to change isolation exercises every six training sessions.

3. The resistance curve of isolation exercises often does not match the resistance curve of compound movements that involve the same muscles. For example, in a squat you are strongest in the top range of the exercise, so a supplemental exercise should give you the most resistance in the bottom range. With a horizontal back extension the most resistance is also at the top range, so this exercise offers little benefit to improving your squat. A better choice would be a 45-degree back extension, as the resistance is greater at the start and mid-range of the movement.

4. Isolation exercises are often more effective when performed from a seated position. Exercising from a seated position conserves neural drive that otherwise would be spent stabilizing the body in a standing position. As an example, studies using EMG (electromyography – a method of measuring the electrical activity of muscles) have found that Scott curls produce greater involvement of the elbow flexors than standing barbell curls.

5. Compound movements often provide a better match between the strength curve and the resistance curve. With many compound movements using a barbell you can often adjust to changes in the body’s natural strength curve by using “cheating” methods. For example, when performing the standing barbell overhead press, when you reach a point of failure you can use your legs to kick the barbell through the sticking point to overload the end range. Also, on the last rep of concentric failure, with the barbell overhead you can lower it slowly, thus prolonging the time under tension to produce a powerful eccentric contraction.

6. Workouts using isolation exercises require more variety. Although workouts that use primarily isolation exercises require more exercises be performed, you still need to plan carefully for optimal results. For example, the one-arm lateral raise with dumbbells is a good exercise for the medial deltoids, but the primary stress is felt in the mid range of the movement. To work all areas of the strength curve, you could also include the lean-away lateral raise with a dumbbell (top range) and the one-arm lateral raise with low cables (bottom range).

7. When training twice a day, compound movements are better for the first session. If you have the time to train twice a day, focus on the compound movements in the first session and the isolation movements in the second. Performing the isolation movements in the first session would significantly reduce the amount of weight you could use in compound exercises performed later that day. To work the pectorals, for example, you could perform bench presses or dips in the first session, and dumbbell flyes in the second.

8. In isolation exercises, it’s generally safer to use free weights and cables. Many exercise machines often force the user into a strict movement pattern that may not be comfortable and could (through a condition called “pattern overload”) increase the risk of overuse injuries – this is especially true with machines that attempt to isolate the arms. Although there are certainly many good exercise machines that can be adjusted to fit an individual’s anatomy, you’ll usually find that dumbbells and cables usually provide a much more natural movement pattern.

The bottom line is that both isolation and compound movements have value. These guidelines can help you determine when to use which type of exercise and how to get the most out of your training.